In a blender or food processor, blend the vinegar with the mustard and shallot until combined. With the machine on, slowly add the oil until the dressing is emulsified. Blend in the sour cream. Transfer the dressing to a small bowl and stir in the tarragon. Season the dressing with salt and pepper.

In a large bowl, toss the smoked chicken with the endives, cucumber, onion, jicama and sun-dried tomatoes. Add the tarragon dressing, season with salt and pepper and toss well. Arrange the arugula on plates and top with the chicken salad. Garnish the salads with the snipped chives and serve.

Notes
If smoked chicken is unavailable, 1 1/2 pounds of smoked turkey can be substituted.